Dipyrenylamine derivatives and electrophotographic photoconductor comprising the same

ABSTRACT

An electrophotographic photoconductor is composed of an electroconductive substrate and a photoconductive layer formed thereon, the photoconductive layer includes a dipyrenylamine derivative of formula (I): ##STR1## wherein R represents an alkyl group with 1 to 12 carbon atoms, which may have a substituent, or an aryl group which may have a substituent. Novel dipyrenylamine derivatives of formula (I), in which R is --ph--(R 4 )n, wherein, ph is a phenyl group, R 4  is hydrogen, an unsubstituted or substituted alkyl group having 1 to 12 carbon atoms, an unsubstituted or substituted alkoxyl group having 1 to 12 carbon atoms, n is an integer of 1 to 5, and when n is 2 to 5, R 4  may be the same or different, which are for use in the photoconductive layer of the electrophotographic photoconductor, are synthesized.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to dipyrenylamine derivatives, methods ofsynthesizing the dipyrenylamine derivatives, and an electrophotographicphotoconductor comprising a photoconductive layer comprising at leastone dipyrenylamine derivative overlaid on an electroconductivesubstrate.

2. Discussion of Background

Conventionally, inorganic materials such as selenium, cadmium sulfideand zinc oxide are used as a photoconductive material of anelectrophotographic photoconductor in the electrophotographic process.The above-mentioned electrophotographic process is one of the imageforming processes, through which the surface of the photoconductor ischarged uniformly in the dark to a predetermined polarity, for instance,by corona charge. The uniformly charged photoconductor is exposed to alight image to selectively dissipate the electrical charge of theexposed areas, so that a latent electrostatic image is formed on thephotoconductor. The thus formed latent electrostatic image is developedby a developer comprising a coloring agent such as a dye and a pigment,and a binder agent such as a polymeric material, to a visible image.

Fundamental characteristics required for the photoconductor for use insuch an electrophotographic process are: (1) chargeability to anappropriate potential in the dark, (2) minimum dissipation of electricalcharge in the dark, and (3) rapid dissipation of electrical charge whenexposed to light.

However, while the above-mentioned inorganic materials have manyadvantages, they have several shortcomings from the viewpoint ofpractical use.

For instance, a selenium photoconductor, which is widely used atpresent, satisfies the above-mentioned requirements (1) to (3)completely, but it has the shortcomings that its manufacturingconditions are difficult and, accordingly, its production cost is high.In addition, it is difficult to work it into the form of a belt due toits poor flexibility, and it is so vulnerable to heat and mechanicalshocks that it must be handled with the utmost care.

A cadmium sulfide photoconductor and a zinc oxide photoconductor can beeasily obtained by coating a dispersion of cadmium sulfide particles andzinc oxide particles respectively in a binder resin on a substrate.However, they are poor in mechanical properties, such as surfacesmoothness, hardness, tensile strength and wear resistance. Therefore,they cannot be used in the repeated operation.

To solve the problems of the inorganic materials, variouselectrophotographic photoconductors employing organic materials havebeen proposed recently and some are put to practical use. For example,there are known a photoconductor comprising poly-N-vinylcarbazole and2,4,7-trinitrofluorene-9-on, as disclosed in U.S. Pat. No. 3,484,237; aphotoconductor prepared by sensitizing poly-N-vinylcarbazole with apigment of pyrylium salt, as described in Japanese Patent Publication48-25658; a photoconductor comprising as the main component an organicpigment, as described in Japanese Laid-Open Patent Application 47-37543;a photoconductor comprising as the main component an eutectic crystalcomplex of a dye and a resin, as described in Japanese Laid-Open PatentApplication 47-10735; a photoconductor prepared by sensitizing atriphenylamine compound with a sensitizer pigment, as described in U.S.Pat. No. 3,180,730; a photoconductor comprising an amine derivative as acharge transporting material, as described in Japanese Laid-Open PatentApplication 57-195254; a photoconductor comprising poly-N-vinylcarbazoleand an amine derivative as charge transporting materials, as describedin Japanese Laid-Open Patent Application 58-1155; and a photoconductorcomprising a polyfunctional tertiary amine compound, in particularbenzidine compound, as a photoconductive material, as described in U.S.Pat. No. 3,265,496, Japanese Patent Publication 39-11546 and JapaneseLaid-Open Patent Application 53-27033.

These electrophotographic photoconductors have their own excellentcharacteristics and considered to be valuable for practical use. Withvarious requirements of the electrophotographic photoconductor inelectrophotography taken into consideration, however, theabove-mentioned conventional electrophotographic photoconductors cannotmeet all the requirements for use in electrophotography.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention to provide anelectrophotographic photoconductor free from the conventionalshortcomings, which can completely satisfy all the requirements in theelectrophotographic process, including high durability, and can beeasily manufactured at relatively low cost.

A second object of the present invention is to provide noveldipyrenylamine derivatives serving as photoconductive materials for usein the above-mentioned electrophotographic photoconductor.

A third object of the present invention is to provide methods ofpreparing the above novel dipyrenylamine derivatives.

The first object of the present invention can be achieved by anelectrophotographic photoconductor comprising an electroconductivesubstrate and a photoconductive layer formed thereon, which comprises adipyrenylamine derivative of formula (I): ##STR2## wherein R representsan alkyl group with 1 to 12 carbon atoms, which may have a substituent,or an aryl group which may have a substituent.

The second object of the present invention can be achieved by adipyrenylamine derivative having formula (II): ##STR3## wherein R⁴represents hydrogen, an alkyl group having 1 to 12 carbon atoms, whichmay have a substituent, an alkoxyl group represented by --OR¹, in whichR¹ represents an alkyl group having 1 to 12 carbon atoms, which may havea substituent, a phenyl group which may have a substituent, or ahalogen; n is an integer of 1 to 5; and when n is 2 to 5, R⁴ may be thesame or different.

The third object of the present invention can be attained by a method ofpreparing a dipyrenylamine derivative having the above formula (II)comprising the step of allowing an aniline derivative having formula(III) to react with a halogenopyrene having formula (IV): ##STR4##wherein R⁴ and n are the same as defined in the formula (II); and Xrepresents a halogen.

The third object of the present invention can also be attained by amethod of preparing a dipyrenylamine derivative of the formula (II)comprising the step of allowing a N-phenyl-1-aminopyrene derivativehaving formula (V) to react with a halogenopyrene having formula (IV):##STR5## wherein R⁴ and n are the same as defined in the formula (II);and X represents a halogen.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an IR spectrum of a dipyrenylamine derivative obtained inPreparation Example 1;

FIG. 2 is an IR spectrum of a dipyrenylamine derivative obtained inPreparation Example 2;

FIG. 3 is an IR spectrum of a dipyrenylamine derivative obtained inPreparation Example 3;

FIG. 4 is a schematic cross-sectional view of a first example of anelectrophotographic photoconductor according to the present invention;

FIG. 5 is a schematic cross-sectional view of a second example of anelectrophotographic photoconductor according to the present invention;

FIG. 6 is a schematic cross-sectional view of a third example of anelectrophotographic photoconductor according to the present invention;

FIG. 7 is a schematic cross-sectional view of a fourth example of anelectrophotographic photoconductor according to the present invention;and

FIG. 8 is a schematic cross-sectional view of a fifth example of anelectrophotographic photoconductor according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electrophotographic photoconductor according to the present inventioncomprises an electroconductive substrate and a photoconductive layerformed thereon, comprising at least one dipyrenylamine derivative offormula (I): ##STR6## wherein R represents an alkyl group which may havea substituent, or an aryl group which may have a substituent.

The dipyrenylamine derivative of the above-mentioned formula (I) can beprepared by allowing a halogenopyrene having formula (IV) to react withan amine derivative having formula (IIIa): ##STR7## wherein X representsa halogen such as bromine or iodine; R is the same as defined in theformula (I).

The dipyrenylamine derivative of the formula (I) can also be prepared byallowing di(1-pyrenyl)amine having formula (IIIb) to react with a halidehaving formula (IVa): ##STR8## wherein X and R are respectively the sameas defined in the formula (IV) and the formula (I).

When R represents an aryl group in the above-mentioned formulas (I),(IIIa) and (IVa), examples of the aryl group include a non-fusedaromatic hydrocarbon group, a fused polycyclic hydrocarbon group and aheterocyclic aromatic hydrocarbon group.

Specific examples of the non-fused aromatic hydrocarbon group are phenylgroup, biphenyl group and terphenyl group.

Specific examples of the fused polycyclic hydrocarbon group arepentalenyl group, indenyl group, naphthyl group, azulenyl group,heptalenyl group, biphenylenyl group, as-indacenyl group, fluorenylgroup, S-indacenyl group, acenaphthylenyl group, pleiadenyl group,acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group,fluoranthenyl group, acephenanthrylenyl group, aceanthrylenyl group,triphenylenyl group, pyrenyl group, chrysenyl group and naphthacenylgroup.

Specific examples of the heterocyclic aromatic hydrocarbon group arethienyl group, furyl group, 2-pyridyl group, 4-pyridyl group, 3-indolylgroup, 2-quinolinyl group, 3,4-benzpyranyl group, acridinyl group,thiazolyl group, benzothiazolonyl group, 9-methylcarbazolyl group,9-ethylcarbazolyl group, 9-propylcarbazolyl group, 9-phenylcarbazolylgroup, 9-tolylcarbazolyl group and 4-pyrazolyl group.

Examples of the substituent of the aryl group represented by R in theformula (I) are as follows:

(1) Halogen, cyano group and nitro group.

(2) An alkyl group having 1 to 12 carbon atoms, more preferably an alkylgroup having 1 to 8 carbon atoms, and further preferably an alkyl grouphaving 1 to 4 carbon atoms, which may have a substituent.

Specific examples of the above alkyl group include methyl group, ethylgroup, n-propyl group, i-propyl group, t-butyl group, s-butyl group,n-butyl group, i-butyl group, 2-hydroxyethyl group, 2-cyanoethyl group,2-ethoxyethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzylgroup, 4-methylbenzyl group, 4-methoxybenzyl group and 4-phenylbenzylgroup.

Specific examples of the substituent of the above alkyl group arehydroxyl group, cyano group, alkoxyl group having 1 to 4 carbon atoms,phenyl group, halogen, phenyl group substituted with alkyl group having1 to 4 carbon atoms, and phenyl group substituted with alkoxyl grouphaving 1 to 4 carbon atoms.

(3) An alkoxyl group represented by --OR¹, in which R¹ represents thesame alkyl group which may have a substituent as defined in (2).

Specific examples of the above alkoxyl group include methoxy group,ethoxy group, n-propoxy group, i-propoxy group, t-butoxy group, n-butoxygroup, s-butoxy group, i-butoxy group, 2-hydroxyethoxy group,2-cyanoethoxy group, benzyloxy group and 4-methylbenzyloxy group.

(4) An aryloxy group, in which an aryl group represents, for example, aphenyl group and a naphthyl group. The above aryloxy group may have asubstituent such as an alkoxyl group having 1 to 4 carbon atoms, analkyl group having 1 to 4 carbon atoms or a halogen.

Specific examples of the above aryloxy group include phenoxy group,1-naphthyloxy group, 2-naphthyloxy group, 4-methylphenoxy group,4-methoxyphenoxy group, 4-chlorophenoxy group and 6-methyl-2-naphthyloxygroup.

(5) An alkylmercapto group represented by --SR¹, in which R¹ representsthe same alkyl group which may have a substituent as defined in (2).

Specific examples of the above alkylmercapto group include methylthiogroup, ethylthio group, phenylthio group and p-methylphenylthio group.

(6) ##STR9## in which R² and R³ independently represent hydrogen, thesame alkyl group which may have a substituent as defined in (2) or anaryl group which may have a substituent. As the aryl group, phenylgroup, biphenyl group or naphthyl group can be employed, which may havea substituent such as an alkoxyl group having 1 to 4 carbon atoms, analkyl group having 1 to 4 carbon atoms or a halogen. R² R³ may form aring in combination or in combination with carbon atoms on the arylgroup.

Specific examples of the above ##STR10## include an amino group,diethylamino group, N-methyl-N-phenylamino group, N,N-diphenylaminogroup, N,N-di(p-tolyl)amino group, dibenzylamino group, piperidinogroup, morpholino group and julolidyl group.

(7) An alkylenedioxy group such as methylenedioxy group, or analkylenedithio group such as methylenedithio group.

When R represents an alkyl group in the previously mentioned formulas(I), (IIIa) and (IVa), the same alkyl group which may have a substituentas defined in (2) of the specific examples of the substituent of thearyl group can be employed.

Specific examples of the dipyrenylamine derivatives according to thepresent invention are shown in the following Table 1:

                  TABLE 1                                                         ______________________________________                                         ##STR11##                                                                    Compound No.                                                                              R                                                                 ______________________________________                                         1          CH.sub.3                                                           2          CH.sub.2 CH.sub.3                                                  3                                                                                         ##STR12##                                                         4                                                                                         ##STR13##                                                         5                                                                                         ##STR14##                                                         6                                                                                         ##STR15##                                                         7                                                                                         ##STR16##                                                         8                                                                                         ##STR17##                                                         9                                                                                         ##STR18##                                                        10                                                                                         ##STR19##                                                        11                                                                                         ##STR20##                                                        12                                                                                         ##STR21##                                                        13                                                                                         ##STR22##                                                        14                                                                                         ##STR23##                                                        15                                                                                         ##STR24##                                                        16                                                                                         ##STR25##                                                        17                                                                                         ##STR26##                                                        18                                                                                         ##STR27##                                                        19                                                                                         ##STR28##                                                        20                                                                                         ##STR29##                                                        21                                                                                         ##STR30##                                                        22                                                                                         ##STR31##                                                        23                                                                                         ##STR32##                                                        24                                                                                         ##STR33##                                                        25                                                                                         ##STR34##                                                        26                                                                                         ##STR35##                                                        27                                                                                         ##STR36##                                                        28                                                                                         ##STR37##                                                        29                                                                                         ##STR38##                                                        ______________________________________                                    

Among the above-mentioned dipyrenylamine derivatives, the followingdipyrenylamine derivatives having formula (II) are novel compounds:##STR39## wherein R⁴ represents hydrogen, an alkyl group having 1 to 12carbon atoms, which may have a substituent, an alkoxyl group representedby --OR¹,in which R¹ represents an alkyl group having 1 to 12 carbonatoms, which may have a substituent, a phenyl group which may have asubstituent, or a halogen; n is an integer of 1 to 5; and when n is 2 to5, R⁴ may be the same or different.

The dipyrenylamine derivative having the above formula (II) can beprepared by allowing an aniline derivative having formula (III) to reactwith a halogenopyrene having formula (IV): ##STR40## wherein R⁴ and nare the same as defined in the formula (II); and X represents a halogen.

The dipyrenylamine derivative of the formula (II) can also be preparedby allowing a N-phenyl-1-aminopyrene derivative having formula (V) toreact with a halogenopyrene having formula (IV): ##STR41## wherein R⁴and n are the same as previously defined in the formula (II); and Xrepresents a halogen.

Examples of the alkyl group which may have a substituent, the alkoxylgroup which may have a substituent, and the phenyl group which may havea substituent represented by R⁴ in the formulas (II), (III) and (V) aresubstantially the same as the specific examples of the correspondingsubstituents of the aryl group represented by R in the formula (I).

More specifically, the alkyl group represented by R⁴ is a lower alkylgroup such as methyl group, ethyl group, propyl group and butyl group.

Specific examples of the alkoxyl group represented by R⁴ include a loweralkoxyl group such as methoxy group, ethoxy group and propoxy group.

The above-mentioned alkyl group and alkoxyl group may have a substituentsuch as phenyl group, a halogen, alkoxyl group and aryloxy group.

The phenyl group represented by R⁴ in the formulas (II), (III) and (V)also may have a substituent such as a lower alkyl group, for instance,methyl group, ethyl group, propyl group and butyl group; a lower alkoxylgroup, for instance, methoxy group, ethoxy group and propoxy group; anda halogen, for instance, bromine, chlorine and fluorine.

Specific examples of the halogen represented by X in the formula (IV)are bromine and iodine.

The dipyrenylamine derivatives of the present invention having formula(II) can be prepared by allowing the previously mentioned anilinederivative having formula (III) to react with the halogenopyrene havingformula (IV), or the N-phenyl-1-aminopyrene derivative having formula(V) to react with the halogenopyrene having formula (IV), in a solventin a stream of nitrogen at about 150° to 250° C. in the presence ofcopper powder, copper oxide or copper halogenide, with an alkaline saltadded thereto in a sufficient amount for neutralizing hydrogenhalogenide generated in the course of the reaction. In this case, thesolvent may not be used in the reaction.

Examples of the above-mentioned alkaline salt used in the reaction aresodium hydroxide, potassium hydroxide, sodium carbonate and potassiumcarbonate. Examples of the solvent used in the reaction arenitrobenzene, dichlorobenzene, quinoline, N,N-dimethylformamide,dimethyl sulfoxide, N-methylpyrrolidone and1,3-dimethyl-2-imidazolidinone.

The above-mentioned novel dipyrenylamine derivatives of the presentinvention, which are remarkably effective as photoconductive materialsin the electrophotographic photoconductor, are optically or chemicallysensitized with a sensitizer such as a dye or Lewis acid. In addition,the dipyrenylamine derivatives effectively function as a chargetransporting material in a function-separating type electrophotographicphotoconductor where an organic or inorganic pigment serves as a chargegenerating material.

In the photoconductors according to the present invention, at least onedipyrenylamine derivative of the formula (I) is contained in thephotoconductive layers 2, 2a, 2b, 2c and 2d. The dipyrenylaminederivatives can be employed in different ways, for example, as shown inFIGS. 4 to 8.

In the photoconductor as shown in FIG. 4, a photoconductive layer 2 isformed on an electroconductive substrate 1, which photoconductive layer2 comprises a dipyrenylamine derivative, a sensitizing dye and a binderagent (binder resin). In this photoconductor, the dipyrenylaminederivative works as a photoconductive material, through which chargecarriers which are necessary for the light decay of the photoconductorare generated and transported. However, the dipyrenylamine derivativeitself scarcely absorbs light in the visible light range and, therefore,it is necessary to add a sensitizing dye which absorbs light in thevisible light range in order to form latent electrostatic images by useof visible light.

Referring to FIG. 5, there is shown a cross-sectional view of anotherembodiment of an electrophotographic photoconductor according to thepresent invention. In the figure, on the electroconductive substrate 1,there is formed a photoconductive layer 2a comprising a chargegenerating material 3 dispersed in a charge transporting medium 4comprising a dipyrenylamine derivative and a binder agent. In thisembodiment, the dipyrenylamine derivative and the binder agent (or amixture of the binder agent and a plasticizer) in combination constitutethe charge transporting medium 4. The charge generating material 3,which is, for example, an inorganic or organic pigment, generates chargecarriers. The charge transporting medium 4 accepts the charge carriersgenerated by the charge generating material 3 and transports thosecharge carriers.

In this electrophotographic photoconductor, it is essential that thelight-absorption wavelength regions of the charge generating material 3and the dipyrenylamine derivative not overlap in the visible lightrange. This is because, in order to have the charge generating material3 produce charge carriers efficiently, it is necessary to allow thelight to reach the surface of the charge generating material 3. Thedipyrenylamine derivatives of formula (I) scarcely absorb the light inthe visible range. Therefore, especially when combined with the chargegenerating material 3 which absorbs the light in the visible region andgenerates charge carriers, the dipyrenylamine derivatives of the presentinvention can work effectively as charge transporting materials.

Referring to FIG. 6, there is shown a cross-sectional view of a furtherembodiment of an electrophotographic photoconductor according to thepresent invention. In the figure, there is formed on anelectroconductive substrate 1 a two-layered photoconductive layer 2bcomprising a charge generation layer 5 containing the charge generatingmaterial 3, and a charge transport layer 4 containing a dipyrenylaminederivative of formula (I).

In this photoconductor, the light which has passed through the chargetransport layer 4 reaches the charge generation layer 5, where chargecarriers are generated. The charge carriers which are necessary for thelight decay for latent electrostatic image formation are generated bythe charge generating material 3, and accepted and transported by thecharge transport layer 4. In the charge transport layer 4, thedipyrenylamine derivative mainly works for transportation of chargecarriers. The generation and transportation of the charge carriers areperformed by the same mechanism as that in the photoconductor shown inFIG. 5.

Referring to FIG. 7, there is shown still another embodiment of anelectrophotographic photoconductor according to the present invention.In the figure, the overlaying order of the charge generation layer 5 andthe charge transport layer 4 is reversed. The mechanism of thegeneration and transportation of charge carriers is substantially thesame as that of the photoconductor shown in FIG. 6.

In the above photoconductor, a protective layer 6 may be formed on thecharge generation layer 5 as shown in FIG. 8 for improving themechanical strength thereof.

When the electrophotographic photoconductor according to the presentinvention as shown in FIG. 4 is prepared, at least one dipyrenylaminederivative of formula (I) is dispersed in a binder resin solution, and asensitizing dye is then added to the mixture, so that a photoconductivelayer coating liquid is prepared. The thus prepared photoconductivelayer coating liquid is coated on an electroconductive substrate i anddried, so that a photoconductive layer 2 is formed on theelectroconductive substrate 1.

It is preferable that the thickness of the photoconductive layer 2 be inthe range of 3 to 50 μm, more preferably in the range of 5 to 20 μm. Itis preferable that the amount of the dipyrenylamine derivative containedin the photoconductive layer 2 be in the range of 30 to 70 wt. %, morepreferably about 50 wt. %.

It is preferable that the amount of the sensitizing dye contained in thephotoconductive layer 2 be in the range of 0.1 to 5 wt. %, morepreferably in the range of 0.5 to 3 wt. %.

Specific examples of the sensitizing dye for use in the presentinvention are: triarylmethane dyes such as Brilliant Green, VictoriaBlue B, Methyl Violet, Crystal Violet and Acid Violet 6B; xanthene dyessuch as Rhodamine B, Rhodamine 6G, Rhodamine G Extra, Eosin S,Erythrosin, Rose Bengale and Fluoresceine; thiazine dyes such asMethylene Blue; cyanine dyes such as cyanin; and pyrylium dyes such as2,6-diphenyl -4-(N,N-dimethylaminophenyl)thiapyrylium perchlorate andbenzopyrylium salts (described in Japanese Patent Publication 48-25658).These sensitizing dyes can be used alone or in combination.

The electrophotographic photoconductor shown in FIG. 5 can be obtainedby dispersing finely-divided particles of the charge generating material3 in the solution in which at least one dipyrenylamine derivative foruse in the present invention and the binder agent are dissolved, coatingthe above-prepared dispersion on the electroconductive substrate 1 andthen drying the same to form the photoconductive layer 2a.

It is preferable that the thickness of the photoconductive layer 2a bein the range of 3 to 50 μm, more preferably in the range of 5 to 20 μm.It is preferable that the amount of the dipyrenylamine derivativecontained in the photoconductive layer 2a be in the range of 10 to 95wt. %, more preferably in the range of 30 to 90 wt. %.

It is preferable that the amount of the charge generating material 3contained in the photoconductive layer 2a be in the range of 0.1 to 50wt. %, more preferably in the range of 1 to 20 wt. %.

Specific examples of the charge generating material 3 are as follows:inorganic pigments such as selenium, selenium-tellurium, cadmiumsulfide, cadmium sulfide-selenium and α-silicone; and organic pigments,such as C.I. Pigment Blue 25 (C.I. 21180), C.I. Pigment Red 41 (C.I.21200), C.I. Acid Red 52 (C.I. 45100), and C.I. Basic Red 3 (C.I.45210); an azo pigment having a carbazole skeleton (Japanese Laid-OpenPatent Application 53-95033), an azo pigment having a distyryl benzeneskeleton (Japanese Laid-Open Patent Application 53-133445), an azopigment having a triphenylamine skeleton (Japanese Laid-Open PatentApplication 53-132347), an azo pigment having a dibenzothiopheneskeleton (Japanese Laid-Open Patent Application 54-21728), an azopigment having an oxadiazole skeleton (Japanese Laid-Open PatentApplication 54-12742), an azo pigment having a fluorenone skeleton(Japanese Laid-Open Patent Application 54-22834), an azo pigment havinga bisstilbene skeleton (Japanese Laid-Open Patent Application 54-17733),an azo pigment having a distyryl oxadiazole skeleton (Japanese Laid-OpenPatent Application 54-2129), and an azo pigment having a distyrylcarbazole skeleton (Japanese Laid-Open Patent Application 54-14967); aphthalocyanine pigment such as C.I. Pigment Blue 16 (C.I. 74100); indigopigments such as C.I. Vat Brown 5 (C.I. 73410) and C.I. Vat Dye (C.I.73030); and perylene pigments such as Algol Scarlet B (made by BayerCo., Ltd.) and Indanthrene Scarlet R (made by Bayer Co., Ltd.). Thesecharge generating materials may be used alone or in combination.

The electrophotographic photoconductor shown in FIG. 6 can be obtainedas follows:

The charge generating material is vacuum-deposited on theelectroconductive substrate 1, or the dispersion in which finely-dividedparticles of the charge generating material 3 are dispersed in anappropriate solvent, together with the binder agent when necessary, iscoated on the electroconductive substrate 1 and dried, so that thecharge generation layer 5 is formed. When necessary, the chargegeneration layer 5 is subjected to surface treatment by buffing andadjustment of the thickness thereof. On the thus formed chargegeneration layer 5, a coating liquid in which at least onedipyrenylamine derivative and the binder agent are dissolved is coatedand dried, so that the charge transport layer 4 is formed. In the chargegeneration layer 5, the same charge generating material as employed inthe previously mentioned photoconductive layer 2a can be used.

The thickness of the charge generation layer 5 is 5 μm or less, morepreferably 2 μm or less. It is preferable that the thickness of thecharge transport layer 4 be in the range of 3 to 50 μm, more preferablyin the range of 5 to 20 μm. When the charge generation layer 5 isobtained by coating the dispersion in which finely-divided particles ofthe charge generating material 3 are dispersed in the binder agent, itis preferable that the amount of finely-divided particles of the chargegenerating material 3 contained in the charge generation layer 5 be inthe range of 10 to 95 wt. %, more preferably in the range of about 50 to90 wt. %. It is preferable that the amount of the dipyrenylaminederivative contained in the charge transport layer 4 be in the range of10 to 95 wt. %, more preferably in the range of 30 to 90 wt. %.

The electrophotographic photoconductor shown in FIG. 7 can be obtainedas follows:

A coating liquid in which the dipyrenylamine derivative and the binderagent are dissolved is coated on the electroconductive substrate 1 anddried to form the charge transport layer 4. On the thus formed chargetransport layer 4, a dispersion prepared by dispersing finely-dividedparticles of the charge generating material 3 in the solvent, in whichthe binder agent is dissolved when necessary, is coated by spray coatingand dried to form the charge generation layer 5 on the charge transportlayer 4. The respective formulations of the charge generation layer andthe charge transport layer are the same as previously described in FIG.6.

The electrophotographic photoconductor shown in FIG. 8 can be obtainedby forming a protective layer 6 on the charge generation layer 5obtained in FIG. 7 by spray-coating an appropriate resin solution. As aresin to be employed in the protective layer 6, any binder agents to bedescribed later can be used.

Specific examples of materials for the electroconductive substrate 1 ofthe electrophotographic photoconductor according to the presentinvention include a metallic plate or foil made of aluminum, a plasticfilm on which a metal such as aluminum is deposited, and a sheet ofpaper which has been treated so as to be electroconductive.

Specific examples of the binder agent for use in the present inventionare condensation resins such as polyamide, polyurethane, polyester,epoxy resin, polyketone and polycarbonate; and vinyl copolymers such aspolyvinylketone, polystyrene, poly-N-vinylcarbazole and polyacrylamide.All the resins having insulating properties and adhesive properties canbe employed.

Some plasticizers may be added to the above-mentioned binder agent, whennecessary. Examples of such plasticizers are halogenated paraffin,polybiphenyl chloride, dimethylnaphthalene and dibutyl phthalate.

Furthermore, in the electrophotographic photoconductors according to thepresent invention, an adhesive layer or a barrier layer can beinterposed between the electroconductive substrate and thephotoconductive layer when necessary. Examples of the material for usein the adhesive layer or the barrier layer are polyamide, nitrocelluloseand aluminum oxide. It is preferable that the thickness of the adhesivelayer or the barrier layer be 1 μm or less.

When copying is performed by use of the photoconductors according to thepresent invention, the surface of the photoconductor is chargeduniformly in the dark to a predetermined polarity. The uniformly chargedphotoconductor is exposed to a light image so that a latentelectrostatic image is formed on the photoconductor. The thus formedlatent electrostatic image is developed by a developer to a visibleimage, and when necessary, the developed image can be transferred to asheet of paper. The electrophotographic photoconductors according to thepresent invention have the advantages in that the photosensitivity ishigh and the flexibility is improved.

Other features of this invention will become apparent in the course ofthe following description of exemplary embodiments, which are given forillustration of the invention and are not intended to be limitingthereof.

Preparation Example 1 [Synthesis of N,N-di(1-pyrenyl)-p-toluidine(Compound No. 9 in Table 1)]

A mixture of 1.07 g (10.0 mmol) of p-toluidine, 6.56 g (20.0 mmol) of1-iodopyrene, 5.53 g of potassium carbonate, 0.64 g of copper powder,and 50 ml of nitrobenzene was subjected to azeotropic dehydration in astream of nitrogen, using an ester tube, with stirring, at 207° C. for6.5 hours.

After the mixture was cooled to room temperature, the resultinginsoluble material of the mixture was removed by filtration by use ofCelite. The thus obtained filtrate was concentrated under the reducedpressure, and nitrobenzene was removed therefrom.

Chloroform was added to the above obtained residue. The chloroform layerwas washed with water and dried with magnesium sulfide. The thusobtained extract was further concentrated under the reduced pressure, sothat an oily dark brown material was obtained.

This oily material was subjected to column chromatography using silicagel as a carrier and a mixed solvent of toluene and n-hexane (1:2) as aneluting solution. The product was recrystallized from a mixed solvent ofethanol and dimethylformamide, so that 1.33 g ofN,N-di(1-pyrenyl)-p-toluidine (Compound No. 9) was obtained as yellowplate crystals with a 26.2% yield. The above compound melted at272.5°-273.5° C.

The results of the elemental analysis of the compound were as follows:

    ______________________________________                                                 % C        % H    % N                                                ______________________________________                                        Calculated 92.28        4.96   2.76                                           Found      92.10        4.81   2.99                                           ______________________________________                                    

The above calculation was based on the formula for N,N-di (1-pyrenyl)-p-toluidine of C₃₉ H₂₅ N.

FIG. 1 shows an infrared spectrum of N,N-di(1-pyrenyl) -p-toluidinetaken by use of a KBr tablet.

Preparation Example 2 [Synthesis of N,N-di(1-pyrenyl)-p-anisidine(Compound No. 15 in Table 1)]

The procedure for preparing N,N-di(1-pyrenyl)-p-toluidine in PreparationExample 1 was repeated except that 10.0 mmol of p-toluidine employed inPreparation Example 1 was replaced by 10.0 mmol of p-anisidine, so thatN,N-di(1-pyrenyl)-p-anisidine of the present invention was obtained.

The above obtained compound melted at 245.5°-246.5° C.

The results of the elemental analysis of the compound were as follows:

    ______________________________________                                                 % C        % H    % N                                                ______________________________________                                        Calculated 89.46        4.81   2.68                                           Found      89.67        4.54   2.58                                           ______________________________________                                    

FIG. 2 shows an infrared spectrum of the above compound taken by use ofa KBr tablet.

Preparation Example 3 [Synthesis of N,N-di(1-pyrenyl)aniline (CompoundNo. 5 in Table 1)]

A mixture of 0.55 g (1.9 mmol) of N-phenyl-1-aminopyrene, 0.92 g (2.8mmol) of 1-iodopyrene, 0.52 g of potassium carbonate, 0.12 g of copperpowder, and 15 ml of nitrobenzene was subjected to azeotropicdehydration in a stream of nitrogen, using an ester tube, with stirring,at 207° C. for 6 hours.

After the mixture was cooled to room temperature, the resultinginsoluble material of the mixture was removed by filtration by use ofCelite. The thus obtained filtrate was concentrated under the reducedpressure, and nitrobenzene was removed therefrom.

The above obtained residue was successively washed with methanol, water,and methanol, so that 0.89 g (96%) of dark green crude crystals wasobtained. The thus obtained crystals were recrystallized fromN,N-dimethylformamide, so that 0.46 g of N,N-di(1-pyrenyl)aniline(Compound No. 5) was obtained as yellow crystals with a 49% yield. Theabove compound melted at 280° C. or more.

The results of the elemental analysis of the compound were as follows:

    ______________________________________                                                 % C        % H    % N                                                ______________________________________                                        Calculated 92.47        4.70   2.83                                           Found      92.53        4.59   2.77                                           ______________________________________                                    

The above calculation was based on the formula for N,N-di(1-pyrenyl)aniline of C₃₈ H₂₃ N.

FIG. 3 shows an infrared spectrum of N,N-di(1-pyrenyl)-aniline taken byuse of a KBr tablet.

EXAMPLE 1

76 parts by weight of Diane Blue (C.I. Pigment Blue 25: C.I. 21180)serving as a charge generating material, 1260 parts by weight of a 2%tetrahydrofuran solution of a polyester resin (Trademark "Vylon 200"made by Toyobo Company, Ltd.) and 3700 parts by weight oftetrahydrofuran were dispersed and ground in a ball mill. The thusprepared dispersion was coated on an aluminum surface of analuminum-deposited polyester film serving as an electroconductivesubstrate by a doctor blade, and dried at room temperature, so that acharge generation layer with a thickness of about 1 μm was formed on theelectroconductive substrate.

2 parts by weight of N,N-di(1-pyrenyl)-p-toluidine (Compound No. 9 inTable 1) prepared in Preparation Example 1 serving as a chargetransporting material, 2 parts by weight of polycarbonate resin(Trademark "Panlite K-1300" made by Teijin Limited.) and 16 parts byweight of tetrahydrofuran were mixed to prepare a coating liquid for acharge transport layer. This liquid was coated on the above formedcharge generation layer by a doctor blade, and dried at 80° C. for 2minutes and then at 120° C. for 5 minutes, so that a charge transportlayer with a thickness of about 20 μm was formed on the chargegeneration layer. Thus an electrophotographic photoconductor No. 1according to the present invention was prepared.

EXAMPLES 2 to 33

The procedure for preparation of the electrophotographic photoconductorNo. 1 in Example 1 was repeated except that Diane Blue serving as acharge generating material for use in the charge generation layer andN,N-di -(1-pyrenyl)-p-toluidine (Compound No. 9) serving as a chargetransporting material for use in the charge transport layer in Example 1were respectively replaced by each of the charge generating materialsand charge transporting materials listed in the following Table 2,whereby electrophotographic photoconductors No. 2 to No. 33 according tothe present invention were prepared.

    TABLE 2        Charge Transporting Material Photoconductor Charge Generating     Material (Dipyrenylamine Derivative No.)      1     ##STR42##      9      2     ##STR43##      9      3     ##STR44##      9      4     ##STR45##      9      5     ##STR46##      9      6     ##STR47##      9      7 β                                                            type      Copper Phthalocyanine 9      8     ##STR48##      15      9     ##STR49##      15   10 P-1 15  11 P-2 15  12 P-3 15  13 P-1 3 14 P-2 3 15 P-3 3 16 P-1     6 17 P-2 6 18 P-3 6 19 P-1 12  20 P-2 12  21 P-3 12  22 P-1 5 23 P-2 5     24 P-3 5 25 P-1 20  26 P-2 20  27 P-3 20  28 P-1 21  29 P-2 21  30 P-3     21  31 P-1 27  32 P-2 27  33 P-3 27

EXAMPLE 34

Selenium was vacuum-deposited on an aluminum plate with a thickness ofabout 300 μm, so that a charge generation layer with a thickness ofabout 1 μm was formed on the aluminum plate.

2 parts by weight of N,N-di(l-pyrenyl)-p-toluidine (Compound No. 9), 3parts by weight of polyester resin (Trademark "Polyester Adhesive 49000"made by Du Pont de Nemours, E. I. & Co.) and 45 parts by weight oftetrahydrofuran were mixed to prepare a coating liquid for a chargetransport layer. This liquid was coated on the above formed chargegeneration layer by a doctor blade, and dried at room temperature andthen under the reduced pressure, so that a charge transport layer with athickness of about 10 μm was formed on the charge generation layer Thusan electrophotographic photoconductor No. 34 according to the presentinvention was prepared.

EXAMPLE 35

The procedure for preparing the electrophotographic photoconductor No.34 in Example 34 was repeated except that a charge generation layer witha thickness of about 0.6 μm was formed on the same aluminum plate asemployed in Example 34 by deposition of the following perylene pigmentinstead of selenium, so that an electrophotographic photoconductor No.35 according to the present invention was prepared: ##STR50##

EXAMPLE 36

1 part by weight of the same Diane Blue as employed in Example 1 and 158parts by weight of tetrahydrofuran were mixed and ground in a ball millto prepare a dispersion. To the thus prepared dispersion, 12 parts byweight of N,N-di(1-pyrenyl)-p-toluidine (Compound No. 9) prepared inPreparation Example 1 and 18 parts by weight of polyester resin(Trademark "Polyester Adhesive 49000" made by Du Pont de Nemours, E. I.& Co.) were added to prepare a coating liquid for a photoconductivelayer. This liquid was coated on an aluminum-deposited polyester filmserving as an electroconductive substrate by a doctor blade, and driedat 100° C. for 30 minutes, so that a photoconductive layer with athickness of about 16 μm was formed on the electroconductive substrate.Thus, an electrophotographic photoconductor No. 36 according to thepresent invention was prepared.

EXAMPLE 37

2 parts by weight of N,N-di(1-pyrenyl)-p-toluidine (Compound No. 9)serving as a charge transporting material, 2 parts by weight ofpolycarbonate resin (Trademark "Panlite K-1300" made by Teijin Limited.)and 16 parts by weight of tetrahydrofuran were mixed to prepare acoating liquid for a charge transport layer. This liquid was coated onan aluminum-deposited polyester film serving as an electroconductivesubstrate by a doctor blade, and dried at 80° C. for 2 minutes and thenat 120° C. for 5 minutes, so that a charge transport layer with athickness of about 20 μm was formed on the electroconductive substrate.

13.5 parts by weight of bisazo pigment (P-2), 5.4 parts by weight ofpolyvinyl butyral (Trademark "XYHL" made by Union Carbide Japan K.K.),680 parts by weight of tetrahydrofuran and 1020 parts by weight of ethylcellosolve were mixed and ground in a ball mill to prepare a dispersion.To this dispersion, 1700 parts by weight of additional ethyl cellosolvewere added and stirred to prepare a coating liquid for a chargegeneration layer. This liquid was coated on the above formed chargetransport layer by spray coating and dried at 100° C. for 10 minutes, sothat a charge generation layer with a thickness of about 0.2 μm wasformed on the charge transport layer.

A methanol/n-butanol solution of a polyamide resin (Trademark "CM-8000"made by Toray Industries, Inc.) was coated on the above formed chargegeneration layer by spray coating and dried at 120° C. for 30 minutes,so that a protective layer with a thickness of about 0.5 μm was formedon the charge generation layer. Thus, an electrophotographicphotoconductor No. 37 according to the present invention was prepared.

Each of the thus prepared electrophotographic photoconductors No. 1 toNo. 37 according to the present invention was charged under applicationof -6 kV or +6 kV of corona charge for 20 seconds, using a commerciallyavailable electrostatic copying sheet testing apparatus ("Paper AnalyzerModel SP-428" made by Kawaguchi Electro Works Co., Ltd.). Then, eachelectrophotographic photoconductor was allowed to stand in the dark for20 seconds without applying any charge thereto, and the surfacepotential Vpo (V) of the photoconductor was measured. Eachphotoconductor was then illuminated by a tungsten lamp in such a mannerthat the illuminance on the illuminated surface of the photoconductorwas 4.5 lux, and the exposure E_(1/2) (lux.sec) required to reduce theinitial surface potential Vpo (V) to 1/2 thereof was measured. Theresults are shown in Table 3.

Furthermore, each of the electrophotographic photoconductors No. 1 toNo. 37 according to the present invention was charged by use of acommercially available electrophotographic copying machine. Then alatent electrostatic image was formed on the photoconductor using anoriginal by illuminating the charged photoconductor. The thus formedlatent electrostatic image was developed by a dry-type developer to avisible image. The thus obtained toner image was electrostaticallytransferred to a sheet of normal paper, so that a clear transferredimage was obtained. A clear image was also obtained when a wet-typedeveloper was employed for development of the latent electrostaticimage.

                  TABLE 3                                                         ______________________________________                                        Photoconductor No                                                                              Vpo (V)  E.sub.1/2  (lux · sec)                     ______________________________________                                        1                -1446    1.51                                                2                -1451    1.67                                                3                -1422    1.01                                                4                -1387    1.17                                                5                -1321    0.80                                                6                -1015    0.52                                                7                -951     1.50                                                8                -1406    1.17                                                9                -1488    1.23                                                10               -1305    0.90                                                11               -1297    0.76                                                12               -921     0.46                                                13               -1521    1.30                                                14               -1451    1.22                                                15               -1389    1.01                                                16               -1351    0.96                                                17               -1259    0.78                                                18               -1002    0.53                                                19               -1361    1.04                                                20               -1231    0.96                                                21               -966     0.60                                                22               -1421    1.10                                                23               -1381    0.97                                                24               -997     0.70                                                25               -1301    0.96                                                26               -127     0.79                                                27               -896     0.49                                                28               -1483    1.15                                                29               -1421    1.01                                                30               -1056    0.77                                                31               -1522    1.30                                                32               -1379    1.38                                                33               -1092    1.22                                                34               -1721    1.56                                                35               -1166    2.41                                                36               +1251    1.62                                                37               +1065    0.92                                                ______________________________________                                    

The electrophotographic photoconductors of the present invention canprovide the improved resistance to heat and mechanical shocks as well asthe photoconductive properties thereof. Furthermore, the photoconductorsaccording to the present invention can be manufactured at low cost.

What is claimed is:
 1. An electrophotographic photoconductor comprisingan electroconductive substrate and a photoconductive layer formedthereon, said photoconductive layer comprising a sensitizer dye and adipyrenylamine derivative of formula (I): ##STR51## wherein R isselected from the group consisting of an alkyl group with 1 to 12 carbonatoms, an aryl group and a heterocyclic aromatic hydrocarbon group, eachof which may have a substituent.
 2. The electrophotographicphotoconductor as claimed in claim 1, wherein said alkyl grouprepresented by R is selected form the group consisting of methyl group,ethyl group, n-propyl group, i-propyl group, t-butyl group, s-butylgroup, n-butyl group, i-butyl group, 2-hydroxyethyl group, 2-cyanoethylgroup, 2-ethoxyethyl group, 2-methoxyethyl group, benzyl group,4-chlorobenzyl group, 4-methylbenzyl group, 4-methoxybenyl group and4-phenylbenzyl group.
 3. The electrophotographic photoconductor asclaimed in claim 1, wherein said substituent of said alkyl grouprepresented by R is selected from the group consisting of hydroxylgroup, cyano group, alkoxyl group having 1 to 4 carbon atoms, phenylgroup, halogen, a phenyl group substituted with an alkyl group having 1to 4 carbon atoms, and a phenyl group substituted with an alkoxyl grouphaving 1 to 4 carbon atoms.
 4. The electrophotographic photoconductor asclaimed in claim 1, wherein said aryl group represented by R is anon-fused aromatic hydrocarbon group.
 5. The electrophotographicphotoconductor as claimed in claim 4, wherein said non-fused aromatichydrocarbon group represented by R is selected from the group consistingof phenyl group, biphenyl group and terphenyl group, which may have asubstituent.
 6. The electrophotographic photoconductor as claimed inclaim 1, wherein said aryl group represented by R is a fused polycyclichydrocarbon group.
 7. The electrophotographic photoconductor as claimedin claim 6, wherein said fused polycyclic hydrocarbon group is selectedfrom the group consisting of a pentalenyl group, indenyl group, naphthylgroup, azulenyl group, heptalenyl group, biphenylenyl group,as-indacenyl group, fluorenyl group, S-indacenyl group, acenaphthylenylgroup, pleiadenyl group, acenaphthenyl group, phenalenyl group,phenanthryl group, anthryl group, fluoranthenyl group,acephenanthrylenyl group, aceanthrylenyl group, triphenylenyl group,pyrenyl group, chrysenyl group and naphthacenyl group.
 8. Theelectrophotographic photoconductor as claimed in claim 1, wherein saidaryl group represented by R is a heterocyclic aromatic hydrocarbongroup.
 9. The electrophotographic photoconductor as claimed in claim 8,wherein said heterocyclic aromatic hydrocarbon group is selected fromthe group consisting of thienyl group, furyl group, 2-pyridyl group,4-pyridyl group, 3-indolyl group, 2-quinolinyl group, 3,4-benzpyranylgroup, acridinyl group, thiazolyl group, benzothiazolonyl group,9-methylcarbazolyl group, 9-ethylcarbazolyl group, 9-propylcarbazolylgroup, 9-phenylcarbazolyl group, 9-tolylcarbazolyl group and 4-pyrazolylgroup.
 10. The electrophotographic photoconductor as claimed in claim 1,wherein said substituent of said aryl group represented by R is selectedfrom the group consisting of halogen, cyano group and nitro group. 11.The electrophotographic photoconductor as claimed in claim 1, whereinsaid substituent of said aryl group represented by R is an alkyl grouphaving 1 to 12 carbon atoms, which may have a substituent.
 12. Theelectrophotographic photoconductor as claimed in claim 11, wherein saidsubstituent of said alkyl group represented by R¹ is selected from thegroup consisting of hydroxyl group, cyano group, an alkoxyl group having1 to 4 carbon atoms, phenyl group, halogen, a phenyl group substitutedwith an alkyl group having 1 to 4 carbon atoms, and a phenyl groupsubstituted with an alkoxyl group having 1 to 4 carbon atoms.
 13. Theelectrophotographic photoconductor as claimed in claim 11, wherein saidalkyl group having 1 to 12 carbon atoms, which may have a substituent,is selected from the group consisting of methyl group, ethyl group,n-propyl group, i-propyl group, t-butyl group, s-butyl group, n-butylgroup, i-butyl group, 2-hydroxyethyl group, 2-cyanoethyl group,2-ethoxyethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzylgroup, 4-methylbenzyl group, 4-methoxy -benzyl group and 4-phenylbenzylgroup.
 14. The electrophotographic photoconductor as claimed in claim 1,wherein said substituent of said aryl group represented by R is analkoxyl group represented by --OR¹ in which R¹ represents an alkyl grouphaving 1 to 12 carbon atoms, which may have a substituent.
 15. Theelectrophotographic photoconductor as claimed in claim 14, wherein saidsubstituent of said alkyl group represented by R¹ is selected from thegroup consisting of hydroxyl group, cyano group, an alkoxyl group having1 to 4 carbon atoms, phenyl group, halogen, a phenyl group substitutedwith an alkyl group having 1 to 4 carbon atoms, and a phenyl groupsubstituted with an alkoxyl group having 1 to 4 carbon atoms.
 16. Theelectrophotographic photoconductor as claimed in claim 14, wherein saidalkoxyl group represented by --OR¹ is selected from the group consistingof methoxy group, ethoxy group, n-propoxy group, i-propoxy group,t-butoxy group, n-butoxy group, s-butoxy group, i-butoxy group,2-hydroxyethoxy group, 2-cyanoethoxy group, benzyloxy group and4-methylbenzyloxy group.
 17. The electrophotographic photoconductor asclaimed in claim 1, wherein said substituent of said aryl grouprepresented by R is an aryloxy group which may have a substituent. 18.The electrophotographic photoconductor as claimed in claim 17, whereinsaid aryloxy group is selected from the group consisting of phenoxygroup and naphthyloxy group.
 19. The electrophotographic photoconductoras claimed in claim 17, wherein said substituent of said aryloxy groupis selected from the group consisting of an alkoxyl group having 1 to 4carbon atoms, an alkyl group having 1 to 4 carbon atoms, and a halogen.20. The electrophotographic photoconductor as claimed in claim 17,wherein said aryloxy group which may have a substituent is selected fromthe group consisting of a phenoxy group, 1-naphthyloxy group,2-naphthyloxy group, 4-methylphenoxy group, 4-methoxyphenoxy group,4-chlorophenoxy group and 6-methyl-2-naphthyloxy group.
 21. Theelectrophotographic photoconductor as claimed in claim 1, wherein saidsubstituent of said aryl group represented by R is an alkylmercaptogroup represented by --SR¹ in which R¹ represents an alkyl group having1 to 12 carbon atoms, which may have a substituent.
 22. Theelectrophotographic photoconductor as claimed in claim 21, wherein saidsubstituent of said alkyl group represented by R¹ is selected from thegroup consisting of hydroxyl group, cyano group, an alkoxyl group having1 to 4 carbon atoms, phenyl group, halogen, a phenyl group substitutedwith an alkyl group having 1 to 4 carbon atoms, and a phenyl groupsubstituted with an alkoxyl group having 1 to 4 carbon atoms.
 23. Theelectrophotographic photoconductor as claimed in claim 21, wherein saidalkylmercapto group represented by --SR¹ is selected from the groupconsisting of methylthio group, ethylthio group, phenylthio group andp-methylphenylthio group.
 24. The electrophotographic photoconductor asclaimed in claim 1, wherein said substituent of said aryl grouprepresented by R is a group of the formula ##STR52## in which R² and R³independently are selected from the group consisting of hydrogen,analkyl group having 1 to 12 carbon atoms, an aryl group, said alkyl andaryl group may have a substituent, and R² and R³, in combination,forming a ring.
 25. The electrophotographic photoconductor as claimed inclaim 24, wherein said substituent of said alkyl group represented by R²or R³ is selected from the group consisting of hydroxyl group, cyanogroup, an alkoxyl group having 1 to 4 carbon atoms, phenyl group,halogen, a phenyl group substituted with an alkyl group having 1 to 4carbon atoms, and a phenyl group substituted with an alkoxyl grouphaving 1 to 4 carbon atoms.
 26. The electrophotographic photoconductoras claimed in claim 24, wherein said aryl group represented by R² or R³is selected from the group consisting of phenyl group, biphenyl groupand naphthyl group.
 27. The electrophotographic photoconductor asclaimed in claim 24, wherein the substituent of said aryl grouprepresented by R² or R³ is selected from the group consisting of analkoxyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 4carbon atoms and a halogen.
 28. The electrophotographic photoconductoras claimed in claim 24 wherein said group represented by ##STR53## isselected from the group consisting of an amino group, diethylaminogroup, N-methyl-N-phenylamino group, N,N-diphenylamino group,N,N-di(p-tolyl)amino group, dibenzylamino group, piperidino group,morpholino group and julolidyl group.
 29. The electrophotographicphotoconductor as claimed in claim 1, wherein said substituent of saidaryl group represented by R is selected from the group consisting cf analkylenedioxy group and an alkylenedithio group.
 30. Theelectrophotographic photoconductor as claimed in claim 29, wherein saidalkylenedioxy group is methylenedioxy group.
 31. The electrophotographicphotoconductor as claimed in claim 29, wherein said alkylenedithio groupis methylenedithio group.
 32. The electrophotographic photoconductor asclaimed in claim 6, wherein said phenyl group with a substituentrepresented by R is a group represented by ##STR54## wherein R⁴ isselected from the group consisting of hydrogen, an alkyl group having 1to 12 carbon atoms, which may have a substituent, an alkoxyl grouprepresented by --OR¹,in which R¹ represents an alkyl group having 1 to12 carbon atoms, which may have a substituent, a phenyl group which mayhave a substituent, or a halogen, n is an integer of 1 to 5, and when nis 2 to 5, R⁴ may be the same or different.
 33. The electrophotographicphotoconductor as claimed in claim 32, wherein said alkyl grouprepresented by R⁴ has 1 to 8 carbon atoms and said alkyl grouprepresented by R¹ has 1 to 8 carbon atoms.
 34. The electrophotographicphotoconductor as claimed in claim 33, wherein said alkyl grouprepresented by R⁴ has 1 to 4 carbon atoms and said alkyl grouprepresented by R¹ has 1 to 4 carbon atoms.
 35. The electrophotographicphotoconductor as claimed in claim 32, wherein said substituent of saidalkyl group represented by R⁴ is selected from the group consisting ofhydroxyl group, cyano group, alkoxyl group having 1 to 4 carbon atoms,phenyl group, a halogen, a phenyl group substituted with an alkyl grouphaving 1 to 4 carbon atoms, and a phenyl group substituted with analkoxyl group having 1 to 4 carbon atoms.
 36. The electrophotographicphotoconductor as claimed in claim 32, wherein said substituent of saidphenyl group represented by R⁴ is selected from the group consisting ofan alkyl group having 1 to 4 carbon atoms, a phenyl group substitutedwith an alkoxyl group having 1 to 4 carbon atoms, and a halogen.
 37. Theelectrophotographic photoconductor as claimed in claim 1, wherein saiddipyrenylamine derivative is in an amount ranging from 30 wt. % to 70wt. % of the entire weight of said photoconductive layer.
 38. Theelectrophotographic photoconductor as claimed in claim 1, wherein saidphotoconductive layer further comprises a sensitizer dye and a binderagent, and has a thickness of 3 μm to 50 μm.
 39. The electrophotographicphotoconductor as claimed in claim 1, wherein said photoconductive layercomprises a charge generating material dispersed in a chargetransporting medium which comprises said dipyrenylamine derivative and abinder agent.
 40. The electrophotographic photoconductor as claimed inclaim 39, wherein the amount of said dipyrenylamine derivative is in therange of 10 wt. % to 90 wt. % of the entire weight of saidphotoconductive layer, and the amount of said charge generating materialis in the range of 0.1 wt. % to 50 wt. % of the entire weight of saidphotoconductive layer.
 41. The electrophotographic photoconductor asclaimed in claim 1, wherein said photoconductive layer comprises acharge generation layer containing a charge generating material, and acharge transfer layer containing said dipyrenylamine derivative as acharge transporting material.
 42. The electrophotographic photoconductoras claimed in claim 41, wherein the amount of said charge generatinglayer is in the range of 10 wt. % to 95 wt. % of the entire weight ofsaid charge generation layer, and the amount of said dipyrenylaminederivative is in the amount of 10 wt. % to 95 wt. % of the entire weightof said charge transport layer.